This invention is directed towards structures for dispensing liquid, pastes, creams, pellets or the like. In particular this invention is directed towards an improved metering chamber or pump structure for the dispenser.
The prior art referenced herein discloses metering chambers having seals disposed relative to piston assemblies which are designed to prevent material within the dispenser such as paste, creams, liquid, pellets or the like (hereinafter liquid) from leaking out from an outlet port or entering through an inlet port when not desired and from leaking out from the area where a handle actuated piston assembly rod enters the metering chamber. Leaking from metering chambers is still a problem of major concern, however. Generally, prior art soap dispensers use elastic seals of various designs which may also be specially compounded to attempt to withstand the degrading effect of harsh chemicals used in many soap formulas. These seals normally rest in grooves on a piston assembly and slide with a piston assembly. These seals depend on their elastic memory to be compressed against a chamber interior surface in order to create a sealing surface. They do not receive compressive forces from the piston assembly or any elements disposed on the piston assembly. With time and effect of many soap products of this type, the seal will physically change and loose its ability to act as an effective sealing member. These seals sliding on grooves of a piston assembly are used to attempt to close off the handle receiving end of the metering chamber and also sometimes the inlet and outlet ports on the chamber.
U.S. Pat. No. 4,493,440 to von Buelow et al. provides examples of such seals. von Buelow includes one seal to close an outlet port in non-actuated state and one seal to continually close a gap at the handle end of a pump chamber. The pump chamber of von Buelow includes two different interior surface diameter sections. The larger interior surface diameter section includes an inlet port with a narrower interior surface diameter section including an outlet port. A spring in von Buelow is disposed outside the pump chamber between a stroke adjustor ring (for adjusting the discharge volume) on the piston rod and a lever. During the static state (FIG. 2), an uncompressed first X-gasket disposed in the groove of the piston closes off the dispenser outlet port. The seal at the handle end of the chamber of von Buelow is made by an uncompressed second X-gasket in the groove of the piston against the larger diameter section of the cylinder. During the dynamic state (FIG. 3), the piston rod closes off the inlet port as it moves the front portion of the piston rod and the first gasket forward to open the outlet port and to dispense one of three different discharge volumes of material out of the cylinder.
U.S. Pat. No. 4,036,406 to Jespersen and DeLuca discloses a single diameter pump cylinder with an inlet port and an outlet port. As illustrated in FIG. 2 of the patent to Jespersen and DeLuca, at the outlet port a nozzle assembly is retained for dispensing liquid when desired and preventing liquid from leaking when no dispensing is desired. The piston assembly attempts to seal off the handle end of the piston with an uncompressed O-ring and groove. In the dynamic state, the piston assembly moves to seal off the inlet port. The spring is compressively biased outside the pump cylinder between a structural support component surrounding the open end of the cylinder and the axially-directed inward face of the piston indexing head.
Also in the patent to Jespersen and DeLuca is a means for adjusting the maximum output of the dispenser to any one of four different volumes. To achieve this function the liquid contacting face of the piston is angled with respect to the piston central axis and two side surfaces of a square piston indexing head of the piston are held in place by indexing tabs of a pivoting handle. Consequently, the piston can be retained in one of four rotational positions so that the position of the piston within the cylinder at which the inlet port will be closed is varied due to the non-perpendicular liquid contacting face of the piston.
To overcome the deficiency of depending on the elastic memory of seals to compress and recover in order to create a tight sealing surface, the present invention is directed towards a very simple mechanical sealing means which depends on a mechanical compressive method to create a seal. Since it is not effected by the harsh elements associated with such systems, the present invention can then allow use of soft inert materials as part of the sealing means.